Nickel complexes bearing 2-(1H-benzimidazol-2-yl)-phenoxy ligands: Synthesis, characterization and ethylene oligomerization

A series of 2-(1H-benzimidazol-2-yl)-phenols and their nickel complexes have been synthesized and characterized by elemental and spectroscopic analysis. The molecular structures of ligand L4 and complex C5 were confirmed by X-ray diffraction analysis. X-ray crystallographic analysis revealed that complex C5 has a six-coordinated distorted octahedral geometry. Upon activation with Et2AlCl, these nickel(II) complexes showed good activity for ethylene oligomerization. When PPh3 was added as an auxiliary ligand to the catalytic system, an increased activity as high as 1.60 × 107 g mol−1 (Ni) h−1 was observed. The ligand environment and reaction conditions remarkably affected the catalytic behavior of these nickel complexes.